What type of holes do reference holes in standard aluminum area-amplitude ultrasonic test blocks contain?

Reference holes in standard aluminum area-amplitude ultrasonic test blocks contain flat-bottomed holes. This design is specifically chosen for several reasons related to the nature of ultrasonic testing.

Flat-bottomed holes serve to create a well-defined echo when ultrasonic waves are transmitted into the test block. The flat surface at the bottom of the hole provides a consistent interface for wave reflection, which is essential for reliable measurements and analysis. These characteristics allow for more accurate calibration and testing, as the echoes produced can be more easily interpreted. Additionally, the flat-bottomed hole geometry minimizes variables that could affect the wave propagation, making the response predictable and reproducible, which is crucial for establishing reference standards in ultrasonic testing.

In contrast, the alternatives such as V-shaped, spherical, or cylindrical holes would not provide the same clarity of echo signals. V-shaped holes would create echoes that are less uniform and may vary with the angle of incidence. Spherical holes introduce curvature, which complicates the reflection dynamics. Cylindrical holes, while possibly reflective, would not provide the distinct flat echo needed for precise amplitude measurements in this testing context. Thus, the use of flat-bottomed holes is essential for standardized and repeatable measurements in ultrasonic testing practices.